Cryptography is the practice and study of logical means used to achieve information confidentiality, integrity and authenticity. It covers, among other things, encryption (making some data unreadable except for those who know a given secret element, called a key), data hashing (in particular for ...

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Using OAuth 2.0 without token storage

I am building a system for a product which requires Authentication and Authorization. Naturally I have chosen using OAuth 2.0 as it is a commonly used protocol and has proven to be useful. I am ...
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3answers
68k views

What's the difference between SSL, TLS, and HTTPS?

I get confused with the terms in this area. What is SSL, TLS, and HTTPS? What are the differences between them?
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1answer
38 views

Permutation based file secure

I have a thought. 1. Take a file. 2. Read number of bytes. If its less than 2048, padd it till 2048 3. Read each byte. And create a single file which contains the particular byte. Give a random name ...
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51 views

How negative are virtual machines (vms) to /dev/urandom?

I looked at the questions here and here. This then piqued my interest as I've recently been involved with looking into FIPS compliance, and in my vm environment /dev/urandom compliance testing ...
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1answer
40 views

Unlock codes for a mobile app

This is for an Android (via Cordova/Phonegap) game project. My goal is to be able to provide a "promo code" that will allow anyone to unlock the game for free, but I want to limit each code to only ...
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1answer
218 views

Requiring 2 keys to access a content

I need to use an external service that can only be accessed by password. I don't like the idea of storing the plaintext password on the server, but AFAIK there's not much I can do. Considering this ...
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1answer
60 views

Hardware Implementation of Encryption Algorithm

In the abstract of the AES-GCM RFC, the following passage is prominently included: [AES-GCM] can be efficiently implemented in hardware for speeds of 10 gigabits per second and above... Is the ...
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4answers
714 views

Why the symmetric key is added to the message?

Yesterday in my class we learnt how to send a message from Alice to Bob with the achieved goals of confidentiality, integrity and authenticity. In order to have a better performance we use a hybrid ...
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1answer
146 views

How to safely use a Key Derivation Function to secure private data - need guidance

I have some secure data created in my client app which I wish to store on the server as backup for the user. The user already has a password to authenticate with the server. The password is never ...
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2answers
123 views

Encrypt with private and decrypt with public

Above picture is captured from iOS Security overview at page 25. The path encrypt with public and decrypt with private makes sense. But the other path, encrypt with private and decrypt with public ...
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2answers
582 views

Authentication: Username (email) and password hashed together in one database field

I am currently developping a platform with a PHP framework for our client. The head of the client's IT department wants us to handle authentication with one database field containing ...
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2answers
66 views

Difference between Second Pre-image Resistance and Collision Resistance in Cryptographic Hash Functions

I am studying the subject from these notes. However it is not clear what is the difference between "Second Pre-image Resistance" and "Collision Resistance" properties of Cryptographic Hash Functions. ...
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1k views

Describe an example of indistinguishability obfuscation or functional encryption

As described in Perfecting the Art of Sensible Nonsense, a major breakthrough in cryptography research was published in the summer of 2013: Candidate Indistinguishability Obfuscation and Functional ...
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2answers
17k views

How secure is Ubuntu's default full-disk encryption?

How secure is the encryption offered by ubuntu (using the disk utility)? What algorithm is used underneath it? If someone could at least provide a link to some documentation or article regarding that ...
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5answers
9k views

Why AES is not used for secure hashing, instead of SHA-x?

As far as I understand, AES is believed to be extremely secure. (I have read somewhere that it would certainly not be broken in the next 20 years, but I am still not sure if the author was serious.) ...
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1answer
119 views

Two takes on PHP two way encryption - which one is preferable?

I need to encrypt some data and have it decrypted on a later point in time. The data is tied to specific users. I've gathered two possible solutions... 1: The first one is derived from the official ...
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2answers
3k views

What actually happens in “low voltage fault attacks”

I understand they are an attack on crypto algorithms as implemented on various processors, but how do they work? The online papers are too complex for me to understand.
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2answers
65 views

Generating encryption key using location data and other hardware data

I'm trying to find information on encryption without key storage, I plan to generate the key using location data, and hardware addresses, so the key is never stored, instead it is generated if the ...
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4answers
1k views

Multiple CAs signing a single Cert/CSR?

Just saw this suggested on Slashdot So I've seen quite a few people wanting a switch to self-signed certs (who IMO mostly don't understand what making that secure actually involves), and an idea ...
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1answer
68 views

Publicly Available API + Sensitive ID/Key Transmission Over HTTP

I've run into a predicament... I'm developing a mobile application that utilizes a server for various things. One portion is that it stores an id/key pair related to accessing and processing ...
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1answer
63 views

Can a known MD5 hash limit the search space for SHA1 collisions?

For a course in game theory, we are dealing with BitTorrent and alternative strategies (roughly alternative clients) we can employ to maximize our download speed. One strategy is to over-report the ...
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0answers
11 views

FEAL-4 Wrong outputs of Round Functions [migrated]

On page 2 of this article, there is example of FEAL-4. At round 2, the input to F (Round Function) is 0x80800000. As F accepts only 4 bytes I divide the input by 2 so that (As I assume the result ...
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4answers
12k views

Recommended # of iterations when using PKBDF2-SHA256?

I'm curious if anyone has any advice or points of reference when it comes to determining how many iterations is 'good enough' when using PBKDF2 (specifically with SHA-256). Certainly, 'good enough' is ...
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0answers
130 views

John the Ripper - Calculating brute force time to crack password

I'm using incremental mode (brute force) mode in John the Ripper to crack Linux MD5 passwords. I'm trying to calculate the time it will take to run through all combinations of 12 passwords (with 12 ...
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42 views

Decentralised password recovery

Are there good/established techniques for password/key recovery in situations without a centralised service? For example: I can imagine a system where a recovery key is generated, split using secret ...
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1answer
4k views

Will double encryption increase the security of cipher vs bruteforce?

Assume I have a function encrypt(mes,key) where mes is the message, and key is the key. The length of key is 64 bits. Last but not least: assume the only way to crack my cipher is a brute-force ...
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1answer
48 views

Figure out if “correct” encryption algorithm was used

Given a database like CryptDB, is it possible to determine whether the data is actually encrypted with the correct (specified) onion? I'll elaborate a bit: CryptDB uses onions (chaining) of ...
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1answer
29 views

OpenSSL -nopad with ECB mode

I was just trying to check if OpenSSL does use PCSK5 as documentation states when I got the following problem. I first encrypted a plaintext and encrypted it using DES-ECB. I was expecting to see ...
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2answers
45 views

Expand key to size of plaintext

I'm taking a cryptology course, and one thing that popped up as an idea was the following: Can't one take a "master" key, and generate a key that is as big as the plaintext, to encrypt the plaintext ...
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1answer
94 views

Can anyone with access to root CA private key decrypt HTTPS traffic?

Can anyone with access to root CA private key decrypt HTTPS traffic of sites using certificate signed by that CA ? and if yes do he need to be man-in-the-middle or just monitoring traffic is ...
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2answers
73 views

How is a cypher algorithm verified?

I've always thought about how the symmetric cyphers are verified. Let say I would invent a new cypher. (actually I don't :-)) How should I rationalize its security to the public? As far as I saw ...
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1answer
24 views

How to store derby database encryption key in HSM?

The Derby Database supports encryption with a key or password. Traditionally this key is stored in the file systems, now I am looking to store and protect this key in the HSM instead, but I couldn't ...
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4answers
1k views

Location to store an encryption key

I'm building a secure system which stores messages on a server in a Postgresql database. The messages are stored encrypted with PHP's openssl_encrypt() function with the AES-256-CBC method. At the ...
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9answers
13k views

Feeding /dev/random entropy pool?

Which way of additionally feeding /dev/random entropy pool would you suggest for producing random passwords? Or, is there maybe a better way to locally create fully random passwords?
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2answers
74 views

Real-world applications of Differential Privacy?

Differentially private techniques guarantee privacy while often permitting accurate answers ...this is something I have been reading up on lately as a means of preserving user ...
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1answer
46 views

Secure shuffles and the rand() function

I'm trying to understand one aspect of a secure shuffle using Fisher-Yates. For reference, here is Fisher-Yates to shuffle an array x of n elements (numbered from 0 to n-1) (from Securing a Shuffle ...
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1answer
327 views

Don't use encryption without message authentication

The text is taken from the famous answer: Lessons learned and misconceptions regarding encryption and cryptology: Don't use encryption without message authentication Alternatively, you can apply ...
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1answer
513 views

adding certificate that resides on smartcard to the microsoft store with private key ownership

how can we solve CryptAcquireCertificatePrivateKey fails with 0x8009200B when adding certificate from smartcard to local user store? in an enrollment system where users generate smartcard certificate ...
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2answers
1k views

Cryptography behind chip based credit cards (smart cards)?

Why are chips safer than magnetic stripes? The answers to the above question explain that the chip based cards can not be cloned as the "secret number" is embedded in the chip and protected by the ...
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2answers
115 views

Why does the finance industry uses 2TDEA instead of 3TDEA?

Why does the finance industry uses 2TDEA instead of 3TDEA; is there any historical reason or technical limitations like the support by HSMs used in the industry? The paper referred to here says ...
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2answers
954 views

Generating one-time tokens from API-key?

I have a web-site for which I'm building a Drupal module that allows the users of that Drupal site to navigate to my web-site directly from the Drupal site. I intend to distribute secret API-keys to ...
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3answers
312 views

Java AES encryption output length

I am trying to encrypt few database columns (string values) using Java AES algorithm. This is to protect certain sensitive data. For some users these data should decrypted. In Java AES encryption, if ...
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6answers
20k views

Most secure password hash algorithm(s)?

What is/are currently the most cryptographically secure hashing algorithm(s)? (available in PHP) Speed is irrelevant, because I'm iterating the hash over a fixed time (rather than a fixed number of ...
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1answer
53 views

Connecting to Oracle Database from VBScript - Hiding Credentials

At work our first level support uses a ticket management system that allows us to add extra functionality via VBScripts that the application invokes. First level support also receives quite a few ...
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5answers
856 views

What voip client support manual encryption?

In pidgin there is a plugin that we can use to encrypt our messages in chat windows .. Is there anything simular for voip (pc to pc) ? any client that support manual encryption for voice data?(linux)
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4answers
979 views

Why secure encrypted data consistency by strong hashing?

Consider the SSH protocol: the SSH packet is like [data, SHA1(data)]. The packet is entirely encrypted by a block cipher. The question is, why do we need a strong hash to protect the packet ...
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108 views

Efficacy of self-made ransomware protection

I was recently wondering about how to circumvent malware such as the infamous Cryptolocker a while back and was wondering about the efficacy of having a set of files with known content in a known ...
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21answers
109k views

XKCD #936: Short complex password, or long dictionary passphrase?

How accurate is this XKCD comic from August 10, 2011? I've always been an advocate of long rather than complex passwords, but most security people (at least the ones that I've talked to) are ...
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4answers
21k views

how safe is the 256 bit encryption used in bank transactions

Most of the banks use a 128 bit or 256 bit encryption. What does this mean? Does it mean that the keys used in ssl are 128 bit long or what? If they are the ssl key lengths then 128 bit rsa keys are ...
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75 views

Encrypting the salt with password [duplicate]

Salts are stored in the plain text and readily available with the hashed passwords if the password database is compromised. What if we encrypt the salt using password itself? Doesn't it make offline ...